Interfacial Stability between Air Electrode and Ceria-Based Electrolyte under Cathodic Polarization in Solid Oxide Fuel Cells

摘要

The stability of interfacial structure between air electrode and ceria-based electrolyte (Sm2O3-CeO2, SDC) was evaluated under various polarization conditions at 1,000 degrees C. This is because the structural change at the interface is strongly related to the diffusion of constituent elements and has the potential to affect the long term stability. In this study, (La,Sr)MnO3 (LSM) and (La,Sr)(Co,Fe)O-3 (LSCF) were applied as air electrodes. The cell with LSM/SDC interface showed the performance enhancement after cathodic polarization for 5 h, accompanied with the change in interfacial structure. The magnitude of the microstructural change as well as activation was dependent on the current density and the oxygen partial pressure. However, the active triple phase boundary (TPB)-length decreased at every condition studied. On the other hand, no appreciable change in interfacial structure was confirmed for the LSCF/SDC system regardless of polarization conditions. In response to this phenomenon, the total TPB-length was almost identical to the active one. The difference in morphological evolution at the interface depending on the electrode material was discussed.